To realize QoS (Quality of Service) in traffic of an SIP (Session Initiation Protocol) application, for example, the following is performed:
(1) Appropriate ToS/DSCP (Type of Service/Differentiated Service Code Point) marking is performed for packets distributed over a session.
(2) Shaping of traffic is performed.
(3) Traffic for which SIP signaling is not completed is subjected to filtering to secure a band, and other control is performed. As QoS information, only band is defined in a band field (b=) of session description protocol (SDP, Session Description Protocol). A system of communicating other QoS information such as marking and shaping directly in SDP is discussed in MMUSIC of IETF (Internet Engineering Task Force) and the like. However, a general method is to assign a value set by an SIP network manager to an SIP application terminal, based on the values of the SDP media field (m=) and the attribute field (a=).
However, there are SIP application terminals in which QoS parameters set by an SIP network manager cannot be set. When terminals in which QoS parameters can be set are not under control of an SIP network manager, terminal users may set different values from those set by an SIP network manager in their own judgment.
Since use of these terminals inhibits proper operation of priority control of SIP applications, QoS control must be performed in network edges.
For example, in the third generation portable network shown in a reference document: X.P0013-012 to X. P0013-014 (3GPP2), since cellular phones as terminals cannot set QoS parameters, QoS setting is performed in PDSN (Packet Data Serving Node) being a network edge.